Double overdrive transmissions

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by alfio, Dec 17, 2023.

  1. alfio

    alfio Light Load Member

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    ok, I think I understand, you're saying better to do both re-gearing and a transmission with more gears. Truck that I'm wanting to this on currently has 4.63 on 19.5 wheels (diameter of 31.9"). It is one of those C3500HD trucks that GM put out, Legit medium duty frame and axles (Dana 80 in the rear) but the engine and trans are not up to the task (6.5L GM diesel with an NV4500). On another thread you said 13 speeds were too much for a 5.9L Cummins and that there were better options for pickups. Granted, mine is not a pickup exactly but something in between a pickup and a full MDT, but what would you recommend? I'm going with a DT360 International which fits an SAE 2 bellhousing so there are options out there (including the 6+1 you mentioned, also not a fan).

    A.
     
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  3. wore out

    wore out Numbered Classic

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    Stick with the RTO 6613
     
  4. W923

    W923 Road Train Member

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    You are going to need to get that rear end ratio down in the low 3s or get taller tires if you’re going to make use of a tranny with a top gear of.8
     
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  5. jamespmack

    jamespmack Road Train Member

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    Ok now that you have given us more info. How in the world are you gonna put a DT engine in this chassis. The C3500HD is a pickup/truck chassis for like bucket trucks. A heavy one ton. Now I know guys who put a 12v Cummins in them. But a DT? It's like 7 inches longer than the Cummins. Not saying you can't. I'm genuinely curious.
     
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  6. ElmerFudpucker

    ElmerFudpucker Road Train Member

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    A DT360 is a little shorter than a 6bt
     
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  7. jamespmack

    jamespmack Road Train Member

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    Wouldn't a DT 466 and 360 be the same dimensions?
     
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  8. ElmerFudpucker

    ElmerFudpucker Road Train Member

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    I wasn’t a great fan of a 6+1 but did like the fuller 6 speed. Which is the route I would go. I have a f900 with a 6bt and an Allison 4 speed. I’d love to change it to a 6 speed. But even like it sits with 4.10 rears on lp 22.5 rubber it will tote 9 ton of gravel. Albeit slow and the Lucas girling juice brakes are sketch as hell with that weight
     
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  9. ElmerFudpucker

    ElmerFudpucker Road Train Member

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    No. A 360 is only 360 cubes. A 466 is comparable to a c model Cummins
     
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  10. jamespmack

    jamespmack Road Train Member

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    I just looked it up. Tried to add my mistake. Seems like the site is having troubles.

    3-4 inches shorter. I never measured one. Worked on alot. Anyhow 13-1400lbs. engine for 185hp. Seems like alot of work. I would think the cummins would be the best answer.
     
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  11. ElmerFudpucker

    ElmerFudpucker Road Train Member

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    It’s probably due to finance. Those 360’s can be had a lot cheaper. Both use the p pump, but you’re right the Cummins is capable of much more. The 360 was a good little engine but were never hugely popular and was never a powerhouse
     
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